JP6377226B1 - Trivalent chromium chemical conversion treatment solution for zinc or zinc alloy substrate and chemical conversion treatment method using the same - Google Patents

Abstract

An object of the present invention is to provide a trivalent chromium chemical conversion treatment solution for zinc or a zinc alloy base material capable of forming a highly corrosion-resistant chemical conversion film with consideration for the environment.
The present invention includes a trivalent chromium ion, a zirconium ion, a nitrate ion, and a chain colloidal silica, and the pH of the treatment liquid is 2.5 to 5.0, which is free from hexavalent chromium. A trivalent chromium chemical conversion treatment solution for zinc or zinc alloy is provided.
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Description

  The present invention relates to a novel chemical conversion treatment liquid for forming a silver-white, uniform haze-free (white haze-free) finished appearance and excellent corrosion resistance conversion coating on the surface of zinc or zinc alloy metal, and The present invention relates to the chemical conversion treatment method used.

Chemical conversion treatment is a technique that has been used for a long time to impart corrosion resistance to metal surfaces, and is still used for surface treatment of aircraft, building materials, automobile parts, and the like. However, the chemical conversion film represented by the chromate chromate chemical conversion treatment contains a part of harmful hexavalent chromium.
Hexavalent chromium is a WEEE (Waste Electrical and Electronic Equipment) directive, a RoHS (Restriction of Hazardous Substances) directive, an ELV (End of Life directive), etc. A chemical conversion treatment liquid using trivalent chromium instead of hexavalent chromium has been actively studied and industrialized (Japanese Patent Laid-Open No. 2003-166074). In particular, a cobalt compound is often used in order to improve corrosion resistance in a hexavalent chromium-free trivalent chromium chemical conversion treatment solution. Cobalt is one of the so-called rare metals, and is not necessarily in a stable supply system due to the expansion of usage or limited production countries. In addition, cobalt chloride, cobalt sulfate, cobalt nitrate, and cobalt carbonate are also applicable to SVHC (Substances of Very High Concerns) of REACH (Registration, Evaluation, Authorization and Restriction of Chemicals) regulations. And there are moves to limit its use.

JP 2003-166074 A JP-A-7-11454

  In view of the current situation as described above, it is an object of the present invention to provide a trivalent chromium chemical conversion treatment solution for zinc or a zinc alloy base material capable of forming a highly corrosion-resistant chemical conversion film with consideration for the environment. And Furthermore, another object of the present invention is to provide a trivalent chromium chemical conversion treatment solution capable of forming a high-quality corrosion resistance equivalent to that of zinc-nickel alloy plating and a good finished appearance without white haze.

As a result of intensive studies to achieve these two problems, the present inventors, in a trivalent chromium chemical conversion treatment solution containing trivalent chromium ions and not containing hexavalent chromium, have a chain shape together with zirconium ions and nitrate ions. By containing colloidal silica, and by setting the pH of the chemical conversion treatment solution to a specific pH range, the surface of zinc and zinc alloy is excellent in corrosion resistance, and has a uniform finish appearance that is silver-white and free of white haze. The present invention has been completed by finding that a chemical conversion treatment liquid capable of forming a chemical conversion film with consideration of the above can be obtained.
That is, the present invention contains trivalent chromium ions, zirconium ions, nitrate ions and chain colloidal silica, and the pH of the treatment liquid is 2.5 to 5.0, which is a hexavalent chromium-free zinc Or the trivalent chromium chemical conversion liquid for zinc alloy base materials is provided.
Moreover, this invention provides the chemical conversion treatment method including making the said chemical conversion treatment liquid contact with zinc or a zinc alloy base material.

  According to the present invention, it is possible to form a chemical conversion film that is excellent in corrosion resistance without containing hexavalent chromium and cobalt, has a uniform finish appearance that is silver-white and has no white haze, and is environmentally friendly. A trivalent chromium chemical conversion treatment liquid for zinc or zinc alloy substrate can be provided.

FIG. 1 is a diagram showing chain colloidal silica and spherical colloidal silica.

The substrate used in the present invention is not particularly limited as long as the surface can be coated with zinc or a zinc alloy. For example, various metals such as iron, nickel, copper, and alloys thereof, or zinc substitution treatment was performed. Examples of the shape of the metal or alloy such as aluminum include various types such as a plate-shaped object, a rectangular parallelepiped, a cylinder, a cylinder, and a spherical object. Specifically, for example, a disc brake caliper can be used.
The base is plated with zinc or a zinc alloy by a conventional method. In order to deposit galvanizing on the substrate, acidic / neutral baths such as sulfuric acid bath, borofluoride bath, potassium chloride bath, sodium chloride bath, ammonium chloride eclectic bath, alkaline baths such as cyanogen bath, zincate bath, pyrophosphate bath, etc. Either bath can be used. An acidic bath is preferable. The zinc alloy plating may be any of alkaline baths such as an ammonium chloride bath and an organic chelate bath.
Examples of the zinc alloy plating include zinc-iron alloy plating, zinc-nickel alloy plating, zinc-cobalt alloy plating, and tin-zinc alloy plating. Zinc-nickel alloy plating is preferable. The thickness of the zinc or zinc alloy plating deposited on the substrate can be arbitrary, but it is 1 μm or more, preferably 5 to 25 μm.
In the present invention, after depositing zinc or zinc alloy plating on the substrate in this manner, if necessary, pretreatment, for example, water washing or water washing, followed by nitric acid activation treatment, the zinc of the present invention or Using a trivalent chromium chemical conversion treatment solution for a zinc alloy substrate, chemical conversion treatment is performed by a method such as immersion treatment.

The trivalent chromium chemical conversion treatment liquid of the present invention does not substantially contain hexavalent chromium ions, contains trivalent chromium ions, zirconium ions, nitrate ions and chain colloidal silica, and the pH of the treatment liquid is 2.5. -5.0.
The trivalent chromium compound that provides trivalent chromium ions is not particularly limited, but is preferably water-soluble. Examples of the trivalent chromium compound include trivalent chromium salts such as chromium chloride, chromium sulfate, chromium nitrate, chromium phosphate, and chromium acetate. Alternatively, hexavalent chromium ions such as chromic acid and dichromate can be reduced to trivalent chromium ions with a reducing agent. These trivalent chromium compounds may be used alone or in combination of two or more. The content of trivalent chromium ions in the treatment liquid is 2 to 200 mmol / L, preferably 5 to 100 mmol / L, and more preferably 10 to 80 mmol / L. By setting the content of trivalent chromium ions in such a range, excellent corrosion resistance can be obtained. In the present invention, the use of trivalent chromium in such a low concentration range is advantageous from the viewpoint of wastewater treatment and economy.
The zirconium compound that provides zirconium ions is not particularly limited, but is preferably water-soluble. Examples of the zirconium compound include zirconium nitrate, zirconium oxynitrate, ammonium zirconium nitrate, zirconyl chloride, zirconyl sulfate, zirconium carbonate, zirconyl ammonium carbonate, potassium zirconyl carbonate, sodium zirconyl carbonate, lithium zirconyl carbonate, zirconium hydrofluoric acid (H ₂ Inorganic zirconium compounds such as ZrF ₆ ) and salts thereof (for example, sodium salt, potassium salt, lithium salt and ammonium salt) or salts thereof, and organic zirconium such as zirconyl acetate, zirconium lactate, zirconium tartrate, zirconium malate, zirconium citrate Compounds. Preferably, the zirconium compound includes zirconium hydrofluoric acid (H ₂ ZrF ₆ ) and salts thereof, such as sodium, potassium, lithium and ammonium salts of zirconium hydrofluoric acid (H ₂ ZrF ₆ ) [(NH ₄ ) ₂ ZrF ₆ ]. These zirconium compounds may be used alone or in combination of two or more. The content of zirconium ions in the treatment liquid is 1 to 300 mmol / L, preferably 2 to 150 mmol / L, and more preferably 5 to 50 mmol / L. By setting the zirconium ion content in such a range, excellent corrosion resistance can be obtained.
In the present invention, the molar ratio of trivalent chromium ion to zirconium ion (trivalent chromium ion / zirconium ion) is preferably 0.1 to 4, more preferably 0.2 to 3.5. More preferably, it is 0.3-3. By setting the molar ratio of trivalent chromium ions to zirconium ions within such a range, a chemical film with excellent appearance and corrosion resistance can be obtained.
The nitrate compound that provides nitrate ions is not particularly limited, but is preferably water-soluble. Examples of nitric acid compounds include nitric acid, ammonium nitrate, sodium nitrate, potassium nitrate, and lithium nitrate. These nitric acid compounds may be used alone or in combination of two or more. The content of nitrate ions in the treatment liquid is 30 to 400 mmol / L, preferably 40 to 300 mmol / L, more preferably 50 to 200 mmol / L. By setting the content of nitrate ions in such a range, excellent appearance and corrosion resistance can be obtained.
In the present invention, the chain colloidal silica is, as shown in FIG. 1, different from the commonly used spherical colloidal silica, in which primary particles of colloidal silica are bonded in a chain form from several to a dozen. The linear colloidal silica may be linear or branched. 5-20 nm is preferable and, as for the average particle diameter of the primary particle of colloidal silica, 10-15 nm is more preferable. In the chain colloidal silica, it is preferable that primary particles are bonded to each other and are continuous to a length of 20 to 200 nm, and more preferably 40 to 100 nm. The length of the chain colloidal silica is the total length of the main chain and the branched chain. The size of the chain colloidal silica is 20 to 200 nm in length. These chain colloidal silicas may be used alone or in combination of two or more. The concentration of the chain silica is 25 to 600 mmol / L, preferably 30 to 450 mmol / L, more preferably 40 to 300 mmol / L. By setting the content of the chain colloidal silica in such a range, an excellent appearance and corrosion resistance can be obtained. Such chain colloidal silica is commercially available. Examples thereof include ST-UP and ST-OUP manufactured by Nissan Chemical Co., Ltd.

The trivalent chromium chemical conversion treatment solution for zinc or zinc alloy substrate of the present invention can form an excellent corrosion-resistant film on the surface of zinc or zinc alloy plating without containing cobalt ions. However, cobalt-on may be further contained. When cobalt ions are contained, the content is preferably 300 mmol / L or less, more preferably 100 mmol / L or less, and even more preferably 50 mmol / L or less. The cobalt compound that provides cobalt ions is not particularly limited, but is preferably water-soluble. Examples of the cobalt compound include cobalt nitrate, cobalt chloride, and cobalt sulfate. These cobalt compounds may be used alone or in combination of two or more.
The trivalent chromium chemical conversion treatment solution for zinc or zinc alloy substrate of the present invention may further contain fluorine ions. The content of fluorine ions is preferably 6 to 1800 mmol / L, and more preferably 30 to 300 mmol / L. The fluorine ion becomes a counter ion of the zirconium ion, and the zirconium ion can be stabilized by setting the content of the fluorine ion in such a range.
The fluorine-containing compound that provides fluorine ions is not particularly limited. Examples of the fluorine-containing compound include hydrofluoric acid, borohydrofluoric acid, ammonium fluoride, hexafluorozirconic hydrogen acid or a salt thereof, and hexafluorozirconic hydrogenic acid or a salt thereof is preferable. These fluorine-containing compounds may be used alone or in combination of two or more.
The trivalent chromium chemical conversion treatment solution for zinc or zinc alloy substrate of the present invention may further contain a water-soluble carboxylic acid or a salt thereof. The content of the water-soluble carboxylic acid or a salt thereof is preferably 0.1 g / L to 10 g / L, more preferably 0.5 g / L to 8 g / L, still more preferably 1 g / L to 5 g / L. is there. By making content of water-soluble carboxylic acid or its salt into such a range, trivalent chromium ion can be stabilized by complex formation with trivalent chromium ion. Preferably, the molar ratio of the trivalent chromium ion to the water-soluble carboxylic acid or salt thereof is 0.5 or more and 1.5 or less.
Water-soluble carboxylic acid is not particularly limited, for example, R ₁ - (COOH) ₂ [R ₁ = C ₀ ~C _8] oxalate which can be represented by, malonic acid, succinic acid, glutaric acid, adipic Examples thereof include dicarboxylic acids such as acid and suberic acid, and oxalic acid and malonic acid in which R ₁ = C ₀ and C ₁ are preferred. Examples of the water-soluble carboxylic acid salt include alkali metal salts such as potassium and sodium, alkaline earth metal salts such as calcium and magnesium, and ammonium salts. These water-soluble carboxylic acids or salts thereof may be used alone or in combination of two or more.

The trivalent chromium chemical conversion treatment solution for zinc or zinc alloy substrate of the present invention further contains a water-soluble metal salt containing a metal selected from the group consisting of Zn, Al, Ti, Mo, V, Ce and W. Also good.
Examples of the water-soluble metal salt include K ₂ TiF ₆ . These water-soluble metal salts may be used alone or in combination of two or more. The content of the water-soluble metal salt is preferably 0.1 g / L to 1.5 g / L, more preferably 0.2 g / L to 1.0 g / L.
The trivalent chromium chemical conversion treatment solution for zinc or zinc alloy substrate of the present invention may further contain a phosphorus compound.
Examples of the phosphorus compound include NaH ₂ PO ₂ (sodium hypophosphite). These phosphorus compounds may be used alone or in combination of two or more. The content of the phosphorus compound is preferably 0.01 g / L to 1.0 g / L, more preferably 0.1 g / L to 0.5 g / L.
The pH of the trivalent chromium chemical conversion treatment solution for zinc or zinc alloy substrate of the present invention is in the range of 2.5 to 5.0, preferably in the range of 3.0 to 4.5, more preferably in the range of 3.0 to 4. .0 range. In order to adjust the pH within this range, an alkaline agent such as an inorganic acid or organic acid such as nitric acid or hydrochloric acid, ammonia, an ammonium salt, caustic alkali, sodium carbonate, potassium carbonate, or ammonium carbonate may be used. By setting the pH within such a range, an excellent appearance and corrosion resistance can be obtained.
The residue of the said component in the trivalent chromium chemical conversion liquid for zinc or zinc alloy base materials of this invention is water.

There is no restriction | limiting in particular as a method of forming a trivalent chromium chemical conversion film on zinc or zinc alloy plating using the trivalent chromium chemical conversion treatment liquid for zinc or zinc alloy base material of this invention, A well-known method is applicable. . For example, a substrate plated with zinc or a zinc alloy is brought into contact with the chemical conversion solution by a method such as immersion. When immersed, the temperature of the chemical conversion treatment liquid at that time is preferably 20 to 60 ° C, more preferably 30 to 40 ° C. The immersion time is preferably 5 to 600 seconds, more preferably 30 to 300 seconds. In addition, in order to activate the zinc or zinc alloy plating surface, it may be immersed in a dilute nitric acid solution (such as 5% nitric acid), dilute sulfuric acid solution, dilute hydrochloric acid solution, dilute hydrofluoric acid solution or the like before the trivalent chromium chemical conversion treatment. . Conditions and processing operations other than those described above can be performed according to conventional hexavalent chromate processing methods.
The trivalent chromium chemical conversion film formed on zinc or zinc alloy plating using the trivalent chromium chemical conversion treatment solution for zinc or zinc alloy substrate of the present invention contains trivalent chromium, zirconium and chain silica, and is hexavalent. Does not contain chrome.
Next, although an example and a comparative example explain the present invention, the present invention is not limited by these.

  In Examples 1 to 5 and Comparative Examples 1 to 4, zincate galvanized (NZ-98 made by Dipsol) was applied to the surface of a 0.5 × 50 × 70 mm matte steel plate as a galvanized test piece. It was used. The galvanized test piece was immersed in a 5% nitric acid aqueous solution at room temperature for 10 seconds, and then thoroughly rinsed with running tap water to clean the surface. Next, the following chemical conversion treatment was performed on the galvanized specimen. The test piece subjected to the chemical conversion treatment was sufficiently washed with tap water and ion-exchanged water, and then allowed to stand for 10 minutes in an electric drying furnace kept at 80 ° C. and dried.

Example 1
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.7 using aqueous ammonia, the test piece was subjected to immersion treatment at 35 ° C. for 60 seconds.
(A) 5.4 g / L of 40% chromium nitrate (9 mmol / L as Cr ³⁺ ion, 27 mmol / L as NO ₃ ^- ion)
(B) Potassium fluorinated zirconate: 2.0 g / L (7 mmol / L as Zr ion)
(C) Ammonium ^{_{nitrate: 4.8g / L (NO 3 -}} 60mmol / L as the ion)
(D) Chain colloidal silica (diameter 40-100 nm): 20.0 g / L (50 mmol / L)
The balance is water.

(Example 2)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 45 ° C. for 40 seconds.
(A) 35% chromium chloride: 9.0 g / L (20 mmol / L as Cr ³⁺ ion)
(B) 40% fluorinated zirconium acid: 7.8 g / L (15 mmol / L as Zr ion)
(C) Sodium nitrate: 7.2 g / L (85 mmol / L as NO ₃ ⁻ ion)
Zinc nitrate hexahydrate: 0.75g / L (NO ₃ ^- ions as 5 mmol / L)
(D) Chain colloidal silica (diameter 40-100 nm): 40.0 g / L (100 mmol / L)
The balance is water.

(Example 3)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 30 seconds.
(A) 40% chromium sulfate: 8.8 g / L (18 mmol / L as Cr ³⁺ ion)
(B) Ammonium hexafluorozirconate: 2.4 g / L (10 mmol / L as Zr ion)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 64.0 g / L (160 mmol / L)
The balance is water.

Example 4
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 20 seconds.
(A) 40% chromium sulfate: 8.8 g / L (18 mmol / L as Cr ³⁺ ion)
(B) Potassium fluorozirconate: 2.8 g / L (10 mmol / L as Zr ion)
(C) Ammonium nitrate: 8.0 g / L (100 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 108.0 g / L (270 mmol / L)
The balance is water.

(Example 5)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 30 seconds.
(A) 40% chromium nitrate: 11.9 g / L (20 mmol / L as Cr ³⁺ ion, 60 mmol / L as NO ₃ ^- ion)
(B) Ammonium hexafluorozirconate: 1.9 g / L (8 mmol / L as Zr ion)
(C) cobalt nitrate hexahydrate: 5.0g / L (Co ions as ^{_{17mmol / L, NO 3 - 34mmol}} / L as the ion)
(D) sodium ^{_{nitrate: 7.2g / L (NO 3 -}} 85mmol / L as the ion)
(E) Chain colloidal silica (diameter 40-100 nm): 64.0 g / L (160 mmol / L)
The balance is water.

(Comparative Example 1)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 3.5 using caustic soda, and then immersed in the test piece at 30 ° C. for 40 seconds.
(A) 40% chromium nitrate: 11.9g / L (Cr as ^{_{20mmol / L, NO 3 - 60mmol}} / L as the ion)
(B) Ammonium hexafluorozirconate: 2.4 g / L (10 mmol / L as Zr ion)
(C) sodium ^{_{nitrate: 3.4g / L (NO 3 -}} 40mmol / L as the ion)
(D) Spherical colloidal silica (diameter 10-15 nm): 26.5 g / L (100 mmol / L)
The balance is water.

(Comparative Example 2)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 2.0 using caustic soda, and then immersed in the test piece at 30 ° C. for 40 seconds.
(A) 35% chromium chloride: 8.1 g / L (18 mmol / L as Cr ³⁺ ion)
(B) ammonium hexafluorozirconate: 2.2 g / L (9 mmol / L as Zr ion)
(C) Sodium nitrate: 7.2 g / L (85 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 64.0 g / L (160 mmol / L)
The balance is water.

(Comparative Example 3)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 2.5 using caustic soda, and then immersed in the test piece at 30 ° C. for 40 seconds.
(A) 40% chromium nitrate: 47.7 g / L (80 mmol / L as Cr ³⁺ ions, 240 mmol / L as NO ₃ ⁻ ions)
(B) Ammonium hexafluorozirconate: 2.4 g / L (10 mmol / L as Zr ion)
(C) cobalt nitrate hexahydrate: 5.0g / L (Co ions as ^{_{17mmol / L, NO 3 - 34mmol}} / L as the ion)
(D) Oxalic acid dihydrate: 3.8 g / L (30 mmol / L as oxalic acid)
Malonic acid: 3.1 g / L (30 mmol / L as malonic acid)
(E) Chain colloidal silica (diameter 40-100 nm): 48.0 g / L (120 mmol / L)
The balance is water.

(Comparative Example 4)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 3.5 using caustic soda, and then immersed in the test piece at 40 ° C. for 30 seconds.
(A) 40% chromium sulfate: 9.8 g / L (20 mmol / L as Cr ³⁺ ion)
(B) ammonium hexafluorozirconate: 2.2 g / L (9 mmol / L as Zr ion)
(C) Cobalt chloride hexahydrate: 4.1 g / L (17 mmol / L as Co ion)
(D) Oxalic acid dihydrate: 3.8 g / L (30 mmol / L as oxalic acid)
Malonic acid: 3.1 g / L (30 mmol / L as malonic acid)
(E) Spherical colloidal silica (diameter 70-100 nm): 26.5 g / L (100 mmol / L)
The balance is water.

  In Examples 6 to 10 and Comparative Examples 5 and 6, acid bath galvanizing (EZ-985CS manufactured by Dipsol) was applied to the surface of a 0.5 × 50 × 70 mm satin steel plate as a galvanized test piece. I used something. The galvanized test piece was immersed in a 5% nitric acid aqueous solution at room temperature for 10 seconds, and then thoroughly rinsed with running tap water to clean the surface. Next, the following chemical conversion treatment was performed on the galvanized specimen. The test piece subjected to the chemical conversion treatment was sufficiently washed with tap water and ion-exchanged water, and then allowed to stand for 10 minutes in an electric drying furnace kept at 80 ° C. and dried.

(Example 6)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 45 ° C. for 40 seconds.
(A) 35% chromium chloride: 9.0 g / L (20 mmol / L as Cr ³⁺ ion)
(B) Ammonium hexafluorozirconate: 2.4 g / L (10 mmol / L as Zr ion)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
Zinc nitrate hexahydrate: 0.75g / L (NO ₃ ^- ions as 5 mmol / L)
(D) Chain colloidal silica (diameter 40-100 nm): 40.0 g / L (100 mmol / L)
The balance is water.

(Example 7)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 30 seconds.
(A) 40% chromium sulfate: 8.8 g / L (18 mmol / L as Cr ³⁺ ion)
(B) Potassium fluorozirconate: 2.6 g / L (9 mmol / L as Zr ion)
(C) Sodium nitrate: 7.2 g / L (85 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 64.0 g / L (160 mmol / L)
The balance is water.

(Example 8)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 20 seconds.
(A) 40% chromium sulfate: 8.8 g / L (18 mmol / L as Cr ³⁺ ion)
(B) 40% fluorinated zirconium acid: 5.2 g / L (10 mmol / L as Zr ion)
(C) Ammonium nitrate: 8.0 g / L (100 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 107.9 g / L (270 mmol / L)
The balance is water.

Example 9
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 30 seconds.
(A) 40% chromium nitrate: 6.0 g / L (10 mmol / L as Cr ³⁺ ion, 30 mmol / L as NO ₃ ^- ion)
(B) Ammonium hexafluorozirconate: 3.6 g / L (15 mmol / L as Zr ion)
(C) Ammonium nitrate: 8.0 g / L (100 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 64.0 g / L (160 mmol / L)
The balance is water.

(Example 10)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 30 seconds.
(A) 35% chromium chloride: 13.6 g / L (30 mmol / L as Cr ³⁺ ion)
(B) Ammonium hexafluorozirconate: 3.6 g / L (15 mmol / L as Zr ion)
(C) cobalt nitrate hexahydrate: 5.0g / L (Co ions as ^{_{17mmol / L, NO 3 - 34mmol}} / L as the ion)
(D) sodium nitrate: 2.6g / L (NO ₃ ^- ions as 30 mmol / L)
(E) Chain colloidal silica (diameter 40-100 nm): 40.0 g / L (100 mmol / L)
The balance is water.

(Comparative Example 5)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 2.0 using caustic soda, and then immersed in the test piece at 40 ° C. for 30 seconds.
(A) 40% chromium nitrate: 23.9 g / L (40 mmol / L as Cr ³⁺ ions, 120 mmol / L as NO ₃ ⁻ ions)
(B) cobalt nitrate hexahydrate: 5.0g / L (Co ions as ^{_{17mmol / L, NO 3 - 34mmol}} / L as the ion)
(C) Oxalic acid dihydrate: 1.9 g / L (15 mmol / L as oxalic acid)
Malonic acid: 1.6 g / L (15 mmol / L as malonic acid)
(D) Spherical colloidal silica (diameter 10-15 nm): 26.5 g / L (100 mmol / L)
The balance is water.

(Comparative Example 6)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 3.5 using caustic soda, and then immersed in the test piece at 30 ° C. for 40 seconds.
(A) 35% chromium chloride: 9.0 g / L (20 mmol / L as Cr ³⁺ ion)
(B) cobalt nitrate hexahydrate: 5.0g / L (Co ions as ^{_{17mmol / L, NO 3 - 34mmol}} / L as the ion)
(C) Malonic acid: 6.2 g / L (60 mmol / L as malonic acid)
(D) sodium nitrate: 1.7g / L (NO ₃ ^- ions as 20 mmol / L)
(E) Spherical colloidal silica (diameter 70-100 nm): 26.5 g / L (100 mmol / L)
The balance is water.

  In Examples 11 and 12 and Comparative Examples 7 and 8, as the zinc-nickel alloy plating test piece, zincate zinc-nickel alloy plating (IZ-250 made by Dipsol) was applied to the surface of a 0.5 × 50 × 70 mm matte steel plate. What gave 9-10 micrometers was used. The following chemical conversion treatment was performed on the zinc-nickel alloy plating test piece. The test piece subjected to the chemical conversion treatment was sufficiently washed with tap water and ion-exchanged water, and then allowed to stand for 10 minutes in an electric drying furnace kept at 80 ° C. and dried.

(Example 11)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.0 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 60 seconds.
(A) 40% chromium sulfate: 9.8 g / L (20 mmol / L as Cr ³⁺ ion)
(B) Ammonium hexafluorozirconate: 3.6 g / L (15 mmol / L as Zr ion)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
Zinc nitrate hexahydrate: 0.75g / L (NO ₃ ^- ions as 5 mmol / L)
(D) Chain colloidal silica (diameter 40-100 nm): 20.0 g / L (50 mmol / L)
The balance is water.

(Example 12)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.0 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 60 seconds.
(A) 40% chromium nitrate: 6.0 g / L (10 mmol / L as Cr ³⁺ ion, 30 mmol / L as NO ₃ ^- ion)
(B) 40% fluorozirconic acid: 10.4 g / L (20 mmol / L as Zr ion)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 40.0 g / L (100 mmol / L)
The balance is water.

(Comparative Example 7)
A chemical conversion treatment solution was prepared as described below, and the pH was set to 3.0 using caustic soda. Then, the test piece was subjected to immersion treatment at 40 ° C for 60 seconds.
(A) 40% chromium sulfate: 9.8 g / L (20 mmol / L as Cr ³⁺ ion)
(B) Ammonium hexafluorozirconate: 3.6 g / L (15 mmol / L as Zr)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
Zinc nitrate hexahydrate: 0.75g / L (NO ₃ ^- ions as 5 mmol / L)
(D) Spherical colloidal silica (diameter 10-15 nm): 13.3 g / L (50 mmol / L)
The balance is water.

(Comparative Example 8)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 4.0 using caustic soda, and then immersed in the test piece at 25 ° C. for 60 seconds.
(A) 35% chromium chloride: 9.0 g / L (20 mmol / L as Cr ³⁺ ion)
(B) cobalt nitrate hexahydrate: 5.0g / L (Co ions as ^{_{17mmol / L, NO 3 - 34mmol}} / L as the ion)
(C) sodium ^{_{nitrate: 3.4g / L (NO 3 -}} 40mmol / L as the ion)
(D) Oxalic acid dihydrate: 2.5 g / L (20 mmol / L as oxalic acid)
The balance is water.

  In Examples 13 to 17 and Comparative Examples 9 to 11, as a galvanized test piece, a disc brake caliper (material FCD-450) was acid bath galvanized (EZ-985CS manufactured by Dipsol) in an amount of 5 to 25 μm (differs depending on the part). ) Used. The galvanized test piece was immersed in a 5% nitric acid aqueous solution at room temperature for 10 seconds, and then thoroughly rinsed with running tap water to clean the surface. Next, the following chemical conversion treatment was performed on the galvanized specimen. The test piece subjected to the chemical conversion treatment was sufficiently washed with tap water and ion-exchanged water, and then allowed to stand for 10 minutes in an electric drying furnace kept at 80 ° C. and dried.

(Example 13)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 45 ° C. for 40 seconds.
(A) 35% chromium chloride: 9.0 g / L (20 mmol / L as Cr ³⁺ ion)
(B) Ammonium hexafluorozirconate: 2.4 g / L (10 mmol / L as Zr ion)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
Zinc nitrate hexahydrate: 0.75g / L (NO ₃ ^- ions as 5 mmol / L)
(D) Chain colloidal silica (diameter 40-100 nm): 40.0 g / L (100 mmol / L)
The balance is water.

(Example 14)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 30 seconds.
(A) 40% chromium sulfate: 8.8 g / L (18 mmol / L as Cr ³⁺ ion)
(B) Potassium fluorozirconate: 2.6 g / L (9 mmol / L as Zr ion)
(C) Sodium nitrate: 7.2 g / L (85 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 64.0 g / L (160 mmol / L)
The balance is water.

(Example 15)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 20 seconds.
(A) 40% chromium sulfate: 8.8 g / L (18 mmol / L as Cr ³⁺ ion)
(B) 40% fluorinated zirconium acid: 5.2 g / L (10 mmol / L as Zr ion)
(C) Ammonium nitrate: 8.0 g / L (100 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 107.9 g / L (270 mmol / L)
The balance is water.

(Example 16)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 30 seconds.
(A) 40% chromium nitrate: 11.9 g / L (20 mmol / L as Cr ³⁺ ion, 60 mmol / L as NO ₃ ^- ion)
(B) Ammonium hexafluorozirconate: 3.6 g / L (15 mmol / L as Zr ion)
(C) Ammonium nitrate: 8.0 g / L (100 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 64.0 g / L (160 mmol / L)
The balance is water.

(Example 17)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.5 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 30 seconds.
(A) 35% chromium chloride: 13.6 g / L (30 mmol / L as Cr ³⁺ ion)
(B) Ammonium hexafluorozirconate: 3.6 g / L (15 mmol / L as Zr ion)
Cobalt nitrate hexahydrate: 5.0g / L (17mmol / L as Co ions, NO ₃ ^- 34mmol / L as the ion)
(C) sodium nitrate: 2.6g / L (NO ₃ ^- ions as 30 mmol / L)
(D) Chain colloidal silica (diameter 40-100 nm): 40.0 g / L (100 mmol / L)
The balance is water.

(Comparative Example 9)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 3.5 using caustic soda, and then immersed in the test piece at 30 ° C. for 40 seconds.
(A) 40% chromium nitrate: 11.9 g / L (20 mmol / L as Cr ³⁺ ion, 60 mmol / L as NO ₃ ^- ion)
(B) Ammonium hexafluorozirconate: 2.4 g / L (10 mmol / L as Zr ion)
(C) sodium ^{_{nitrate: 3.4g / L (NO 3 -}} 40mmol / L as the ion)
(D) Spherical colloidal silica (diameter 10-15 nm): 26.5 g / L (100 mmol / L)
The balance is water.

(Comparative Example 10)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 2.0 using caustic soda, and then immersed in the test piece at 40 ° C. for 30 seconds.
(A) 40% chromium nitrate: 23.9 g / L (40 mmol / L as Cr ³⁺ ions, 120 mmol / L as NO ₃ ⁻ ions)
(B) cobalt nitrate hexahydrate: 5.0g / L (Co ions as ^{_{17mmol / L, NO 3 - 34mmol}} / L as the ion)
(C) Oxalic acid dihydrate: 1.9 g / L (15 mmol / L as oxalic acid)
Malonic acid: 1.6 g / L (15 mmol / L as malonic acid)
(D) Chain colloidal silica (diameter 40-100 nm): 40.0 g / L (100 mmol / L)
The balance is water.

(Comparative Example 11)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 3.5 using caustic soda, and then immersed in the test piece at 30 ° C. for 40 seconds.
(A) 35% chromium chloride: 9.0 g / L (20 mmol / L as Cr ³⁺ ion)
(B) Ammonium hexafluorozirconate: 2.4 g / L (10 mmol / L as Zr ion)
(C) Cobalt chloride hexahydrate: 4.1 g / L (17 mmol / L as Co ion)
(D) Malonic acid: 6.2 g / L (60 mmol / L as malonic acid)
(E) Spherical colloidal silica (diameter 40-100 nm): 26.5 g / L (100 mmol / L)
The balance is water.

  In Examples 18 and 19 and Comparative Examples 12 and 13, as a zinc-nickel alloy plating test piece, 5 to 25 μm of acid zinc-nickel alloy plating (IZA-2500 made by Dipsol) was applied to a disc brake caliper (material FCD-450). (There is a difference depending on the part) used. The following chemical conversion treatment was performed on the zinc-nickel alloy plating test piece. The test piece subjected to the chemical conversion treatment was sufficiently washed with tap water and ion-exchanged water, and then allowed to stand for 10 minutes in an electric drying furnace kept at 80 ° C. and dried.

(Example 18)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.0 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 60 seconds.
(A) 40% chromium sulfate: 4.9 g / L (10 mmol / L as Cr ³⁺ ion)
(B) ammonium hexafluorozirconate: 1.7 g / L (7 mmol / L as Zr ion)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
Zinc nitrate hexahydrate: 0.75g / L (NO ₃ ^- ions as 5 mmol / L)
(D) Chain colloidal silica (diameter 40-100 nm): 20.0 g / L (50 mmol / L)
The balance is water.

(Example 19)
A chemical conversion treatment solution was prepared as described below, and after adjusting the pH to 3.0 using aqueous ammonia, the test piece was subjected to immersion treatment at 40 ° C. for 60 seconds.
(A) 40% chromium nitrate: 3.0 g / L (5 mmol / L as Cr ³⁺ ion, 15 mmol / L as NO ₃ ^- ion)
(B) 40% fluorinated zirconium acid: 5.2 g / L (10 mmol / L as Zr ion)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
(D) Chain colloidal silica (diameter 40-100 nm): 40.0 g / L (100 mmol / L)
The balance is water.

(Comparative Example 12)
A chemical conversion treatment solution was prepared as described below, and the pH was set to 3.0 using caustic soda. Then, the test piece was subjected to immersion treatment at 40 ° C for 60 seconds.
(A) 40% chromium sulfate: 4.9 g / L (10 mmol / L as Cr ³⁺ ion)
(B) ammonium hexafluorozirconate: 1.7 g / L (7 mmol / L as Zr ion)
(C) Ammonium nitrate: 12.0 g / L (150 mmol / L as NO ₃ ⁻ ion)
Zinc nitrate hexahydrate: 0.75g / L (NO ₃ ^- ions as 5 mmol / L)
(D) Spherical colloidal silica (diameter 10-15 nm): 13.3 g / L (50 mmol / L)
The balance is water.

(Comparative Example 13)
A chemical conversion treatment solution was prepared as described below, adjusted to pH = 4.0 using caustic soda, and then immersed in the test piece at 25 ° C. for 60 seconds.
(A) 35% chromium chloride: 9.0 g / L (20 mmol / L as Cr ³⁺ ion)
(B) cobalt nitrate hexahydrate: 5.0g / L (Co ions as ^{_{17mmol / L, NO 3 - 34mmol}} / L as the ion)
(C) sodium ^{_{nitrate: 3.4g / L (NO 3 -}} 40mmol / L as the ion)
(D) Oxalic acid dihydrate: 2.5 g / L (20 mmol / L as oxalic acid)
The balance is water.

The appearance of the chemical conversion film was evaluated from the viewpoints of color tone, uniformity, and gloss. The evaluation criteria for the color tone are as follows.
(Good) Silver white>Blue> Interference color> White (Poor)
The evaluation criteria for uniformity are as follows.
Good: Trivalent chrome conversion coating has no white haze and uniform finish Impossible: Trivalent chrome conversion coating has white haze, non-uniform finish. (Hereinafter referred to as SST), and corrosion resistance was evaluated by white rust generation time and red rust generation time every 24 hours.

Table 1 shows the results of Examples 1 to 5, Table 2 shows the results of Examples 6 to 10, Table 3 shows the results of Examples 11 and 12, Table 4 shows the results of Examples 13 to 17, and Examples. The results of 18 and 19 are in Table 5, the results of Comparative Examples 1 to 4 are in Table 6, the results of Comparative Examples 5 and 6 are in Table 7, the results of Comparative Examples 7 and 8 are in Table 8, and the Comparative Examples 9 to The results of 13 are shown in Table 9.

Claims (7)

A hexavalent chromium-free 3 for zinc or zinc alloy characterized by containing trivalent chromium ions, zirconium ions, nitrate ions and chain colloidal silica, and having a treatment solution having a pH of 2.5 to 5.0. Chromium chemical conversion solution.   The chemical conversion treatment liquid according to claim 1, wherein the trivalent chromium ion concentration in the treatment liquid is in the range of 2 to 200 mmol / L and the zirconium ion concentration is in the range of 1 to 300 mmol / L.   The chemical conversion treatment solution according to any one of claims 1 to 2, wherein the concentration of the chain colloidal silica in the treatment solution is in the range of 25 to 600 mmol / L.   The chemical conversion treatment solution according to claim 1, wherein the concentration of nitrate ions in the treatment solution is in the range of 30 to 400 mmol / L.   5. The chemical conversion treatment solution according to claim 1, wherein a molar ratio of trivalent chromium ions to zirconium ions (trivalent chromium ions / zirconium ions) is 0.1 to 4. 5.   The chemical conversion treatment solution according to any one of claims 1 to 5, wherein the treatment solution does not contain cobalt ions.   A chemical conversion treatment method comprising contacting the chemical conversion treatment liquid according to claim 1 with zinc or a zinc alloy surface.

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